Shake correction apparatus and control method thereof

ABSTRACT

A shake correction apparatus comprises a shake detection unit which detects a shake of an image capture apparatus, a calculation unit which calculates a shake correction amount for correcting an image blur based on an output from the shake detection unit, a shake correction unit which corrects the image blur based on the shake correction amount, a shake level determination unit which determines a shake level of the image capture apparatus based on an output from the shake detection unit, an offset determination unit which determines an offset value based on the shake correction amount and the shake level, and a subtraction unit which subtracts the offset value from the output from the shake detection unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation of application Ser. No. 13/722,090,filed Dec. 20, 2012, which is a continuation of application Ser. No.13/009,521, filed Jan. 19, 2011, now U.S. Pat. No. 8,351,772, the entiredisclosures of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image stabilizing technique againstthe blur of a captured image caused by the motion of an image captureapparatus.

2. Description of the Related Art

Recently, as image capture apparatuses are becoming more compact with alarger number of pixels and higher magnification of the zoom lens, themotion of the image capture apparatus during exposure, called camerashake, is becoming a serious cause of degrading the quality of acaptured image. There has been proposed a shake correction apparatuswhich reduces the influence of camera shake on a captured image.

For example, Japanese Patent No. 3186219 discloses a method ofsuppressing the response characteristic of a shake correction functionwith respect to the frequency component of panning when it is determinedthat the image capture apparatus is panned, that is, movedintentionally. However, the frequency band of the panning operation isabout DC to 1 Hz, and is very close to a frequency band of 1 Hz to 10 Hzfor the camera shake and body swing. Thus, the following problem arisesin the conventional technique disclosed in Japanese Patent No. 3186219.

More specifically, even a signal having the frequency component of thecamera shake or the body swing during walking or the like is greatlyattenuated, impairing the shake correction effect.

Especially in image capturing during walking, a shake generated by thebody swing is transmitted to the image capture apparatus, increasing theshake amplitude. It becomes difficult to determine whether the imagecapture apparatus is intentionally moved for panning, or a shake isgenerated by the body swing during walking.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above problems, andsuppresses degradation of the shake correction effect even when theamplitude of camera shake in image capturing during walking or the likeis large.

According to a first aspect of the present invention, there is provideda shake correction apparatus comprising: a shake detection unit whichdetects a shake of an image capture apparatus; a calculation unit whichcalculates a shake correction amount for correcting an image blur basedon an output from the shake detection unit; a shake correction unitwhich corrects the image blur based on the shake correction amount; ashake level determination unit which determines a shake level of theimage capture apparatus based on an output from the shake detectionunit; an offset determination unit which determines an offset valuebased on the shake correction amount and the shake level; and asubtraction unit which subtracts the offset value from the output fromthe shake detection unit.

According to a second aspect of the present invention, there is provideda method of controlling a shake correction apparatus including a shakecorrection unit which corrects an image blur, the method comprising: ashake detection step of detecting a shake of an image capture apparatus;a calculation step of calculating a shake correction amount forcorrecting an image blur based on an output from the shake detectionstep; a shake correction step of driving the shake correction unit basedon the shake correction amount; a shake level determination step ofdetermining a shake level of the image capture apparatus based on anoutput from the shake detection step; an offset determination step ofdetermining an offset value based on the shake correction amount and theshake level; and a subtraction step of subtracting the offset value fromthe output from the shake detection step.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the arrangement of a shake correctionapparatus according to the first embodiment of the present invention;

FIGS. 2A to 2C are graphs showing time-series data of a shake levelcalculated by the shake state determination unit of the shake correctionapparatus shown in FIG. 1;

FIGS. 3A and 3B are graphs for explaining processing by an offsetcalculation unit shown in FIG. 1;

FIG. 4 is a flowchart for explaining processing by the offsetcalculation unit shown in FIG. 1;

FIG. 5 is a table for explaining processing by the offset calculationunit shown in FIG. 1;

FIGS. 6A to 6D are views for explaining the effect of the shakecorrection apparatus in the first embodiment;

FIGS. 7A to 7D are views for explaining the effect of the shakecorrection apparatus in the first embodiment;

FIG. 8 is a flowchart showing processing by the shake statedetermination unit of a shake correction apparatus in the secondembodiment;

FIGS. 9A to 9C are graphs showing time-series data of a shake levelcalculated by the shake state determination unit of the shake correctionapparatus shown in FIG. 8;

FIG. 10 is a block diagram showing the arrangement of a shake correctionapparatus according to the third embodiment; and

FIG. 11 is a graph for explaining the operation of a variable gaincalculation unit shown in FIG. 10.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

FIG. 1 is a block diagram showing the arrangement of a shake correctionapparatus according to the first embodiment of the present invention.The following embodiments assume a case in which an image captureapparatus such as a digital camera uses the shake correction apparatus.

A shake detection sensor 101 which detects the shake of the shakecorrection apparatus and outputs shake information is an angularvelocity sensor in the embodiment. The shake detection sensor 101 isattached to the shake correction apparatus or the main body of the imagecapture apparatus (not shown). The shake detection sensor 101 detects ashake applied to the apparatus, and detects the magnitude of the shakeas an angular velocity. An A/D (Analog/Digital) converter 102 convertsan angular velocity signal (output value from the shake detection sensor101) into a digital angular velocity signal, and outputs the digitalangular velocity signal. An HPF (High-Pass Filter) 103 removeslow-frequency components equal to or lower than a set low cutofffrequency out of the frequency components of the digital angularvelocity signal output from the A/D converter 102, and outputshigh-frequency components exceeding the low cutoff frequency.

A subtracter 104 subtracts, from the angular velocity signal output fromthe HPF 103, an output from an offset calculation unit 115. Morespecifically, a shake state determination unit (shake leveldetermination unit) 114 outputs, as a shake level, an amount indicatingthe shake state of the image capture apparatus based on the angularvelocity signal output from the HPF 103. The offset calculation unit 115generates a signal for returning the shake correction amount to thecorrection center position in accordance with the shake level and ashake correction amount (output data of sampling of one preceding cycle)calculated by a target position calculation unit 108. Then, the offsetcalculation unit 115 outputs the signal to the subtracter 104. Detailsof the operations of the shake state determination unit 114 and offsetcalculation unit 115 will be described later.

An integrator 105 integrates the high-frequency components of the offsetamount-subtracted angular velocity output from the subtracter 104, andoutputs the integral result as an angle signal. The target positioncalculation unit 108 calculates a shake correction amount for correctingthe shake of the optical axis of an image sensor, based on objectdistance information 106 and focal length information 107 of the zoomlens of the image capture apparatus (not shown), and the angle amountoutput from the integrator 105. A shake correction unit 109 corrects theshake of the optical axis of the image capture apparatus in accordancewith the shake correction amount.

Note that the shake correction unit 109 in the embodiment decenters theoptical axis by driving a correction lens 113 of the correction opticalsystem serving as part of the imaging optical system (lens unit) in adirection perpendicular to the optical axis in accordance with the shakecorrection amount. As a result, the shake correction unit 109 functionsas an optical shake correction unit which corrects the blur of acaptured image. The shake correction unit 109 may also be an electronicshake correction unit which corrects the image blur by moving thereadout region of the image sensor of the image capture apparatus inaccordance with the shake correction amount. Alternatively, the shakecorrection unit 109 may be a sensor shift shake correction unit whichmoves the image sensor within a plane perpendicular to the optical axisin accordance with the shake correction amount.

In this case, the correction lens 113 needs to be driven to correct theshake of the optical axis of the image sensor in accordance with theshake correction amount from the target position calculation unit 108.For this purpose, an anti-vibration lens position control unit 110feedback-controls the position of the correction lens 113 that isdetected by a lens position detection sensor 112. A driving circuit 111drives the correction lens 113 by the shake correction amount from thetarget position calculation unit 108.

Next, the operations of the shake state determination unit 114 andoffset calculation unit 115 in the first embodiment will be explained.

The shake state determination unit 114 outputs, as a shake level, anamount indicating the shake state of the image capture apparatus basedon an angular velocity signal output from the HPF 103. The offsetcalculation unit 115 generates a signal for returning the shakecorrection amount to the correction center position in accordance withthe shake level and a shake correction amount (output data of samplingof one preceding cycle) calculated by the target position calculationunit 108. Then, the offset calculation unit 115 outputs the signal tothe subtracter 104.

Calculation executed in the shake state determination unit 114 will bedescribed. An absolute value converter (absolute value calculation unit)202 outputs the absolute value of an angular velocity output from theHPF 103. An LPF (Low-Pass Filter) 203 removes high-frequency componentsexceeding a set cutoff frequency out of the signal frequency componentsof the absolute value of the angular velocity output from the absolutevalue converter 202, and outputs low-frequency components equal to orlower than the cutoff frequency.

FIGS. 2A to 2C show time-series data of a shake level calculated by theshake state determination unit 114. FIG. 2A shows an angular velocitysignal output from the HPF 103. FIG. 2B shows the absolute value of theangular velocity output from the absolute value converter 202. FIG. 20shows a shake level output from the LPF 203. The amplitude of thedetected angular velocity is small during time ΔTime1, and the camerashake is small as if the user captured an image while holding the imagecapture apparatus with his hands intentionally not to shake it. Theamplitude of the detected angular velocity is large during time ΔTime2,and the camera shake is very large owing to image capturing duringwalking or the like. During time ΔTime3, the amplitude of the angularvelocity is an intermediate one between the amplitude during ΔTime1 andthat during ΔTime2. During time ΔTime4, the user intentionally moves(pans or tilts) the image capture apparatus to, for example, change itscomposition.

In this way, a shake level signal as shown in FIG. 20 can be detected bythe control block in FIG. 1, and it can be detected whether the shake islarge in an image capturing state such as image capturing duringwalking.

From the shake level calculated in the above manner, and the shakecorrection amount of sampling of one preceding cycle, the offsetcalculation unit 115 calculates and generates a signal for returning theshake correction amount to the correction center position. The offsetcalculation unit 115 in the first embodiment calculates and outputs anoffset signal for returning the shake correction amount to thecorrection center position, by using an offset table 201 based on thetwo inputs, that is, the calculated shake level and the shake correctionamount of sampling of one cycle.

FIGS. 3P and 3B exemplify the offset table 201 in the offset calculationunit 115. FIG. 3A is a 3D graph of an offset table which outputs anoffset signal Offset Output set along the Z-axis in accordance with twoinputs, that is, a shake correction amount Lens Position set along theX-axis and a shake level Shake Level set along the Y-axis. FIG. 3B showsan offset table whose input is the shake correction amount Lens Positionalong the X-axis and whose output is the offset signal Offset Outputalong the Z-axis. As shown in FIG. 20, several shake level thresholdsShake Level 1, Shake Level 2, Shake Level 3, and Shake Level 4 are setin advance. By looking up the table of the shake correction amount inputand offset signal output in accordance with the shake level, as shown inFIG. 3B, an offset value is calculated by linear interpolation andoutput.

FIG. 4 is a flowchart showing a method of calculating an output from theoffset table 201 in the offset calculation unit 115. FIG. 5 shows anoffset table map. Note that processing to be described below withreference to FIG. 4 is repetitively executed in every sampling cycleduring a predetermined period.

In step S101, the offset calculation unit 115 calculates four thresholdpoints for the shake correction amount (output data of sampling of onepreceding cycle), based on the focal length information 107. The fourthreshold points are LensPositionThresh[0], LensPositionThresh[1],LensPositionThresh[2], and LensPositionThresh[3].

In step S102, the offset calculation unit 115 calculates four thresholdpoints for a shake level output from the shake state determination unit114, based on the focal length information 107. The four thresholdpoints are ShakeLevelThresh[0], ShakeLevelThresh[1],ShakeLevelThresh[2], and ShakeLevelThresh[3].

In step S103, the offset calculation unit 115 compares the shakecorrection amount LensPosition of one preceding cycle with the fourcalculated threshold points LensPositionThresh, and sets a column to belooked up in the offset table map of FIG. 5. At this time, when theshake correction amount LensPosition of one preceding cycle ispositioned between LensPositionThresh[1] and LensPositionThresh[2],column 2 is selected.

In step S104, the offset calculation unit 115 compares the shake levelShakeLevel with the four calculated threshold points ShakeLevelThresh,and sets a row to be looked up in the offset table map of FIG. 5. Atthis time, when the shake level ShakeLevel is a value equal to or largerthan ShakeLevelThresh[3], row D is selected.

In step S105, the offset calculation unit 115 calculates an offset valueOffsetOutput by looking up the offset table map of FIG. 5 in accordancewith the column and row set in steps S103 and S104. Since the column is2 and the row is D in the above example, D2 is selected and output asthe output value OffsetOutput.

In the above example, the offset table map is directly looked up.However, it is desirable to interpolate the interval between values setin the offset table and output an offset value.

Control in the first embodiment will be explained with reference toFIGS. 6A to 6D and 7A to 7D. FIGS. 6A to 6D exemplify a case in whichthe shake state is not determined, an offset value is output byuniformly looking up the same offset table based on only the shakecorrection amount, and image stabilizing control is performed.

FIG. 6A shows time-series data of an ideal shake correction amount whenthe shake of the image capture apparatus that is detected by the shakedetection sensor 101 is ideally corrected, and time-series data of ashake correction amount when the offset in FIG. 6B is applied. In rangeA, the difference between the ideal value of the shake correction amountand the offset-applied shake correction amount is small, and asatisfactory image stabilizing effect is obtained. However, in range B,the shake is generated to exceed the movable range of shake correctionand cannot be ideally corrected. The offset table in FIG. 6B is set sothat the offset amount is very small for a small shake correction amountand abruptly increases from a range where the shake correction amountgreatly increases. This condition is preferable when the shakecorrection amount is small as in range A because the correction effectis obtained. However, in range B where the shake may be generated toexceed the movable range of image blur correction such as imagestabilizing in, for example, moving image capturing during walking, aman feels the shake caused by the image blur of the image sensor to bemore uncomfortable under this condition. This is because the shakehardly remains thanks to the image stabilizing effect up to a givenshake correction range, but when the shake exceeds the given shakecorrection range, it cannot be corrected suddenly. In other words, thedifferential value of the difference between the ideal value of theshake correction amount and the shake correction amount, that is, themagnitude of the motion vector of the image on the image sensor abruptlychanges from a given range. As a result, the shake speed or shakeacceleration greatly increases, and a man feels the shake to be moreuncomfortable when he views the image.

FIG. 6C shows time-series data of an ideal shake correction amount whenthe shake of the image capture apparatus that is detected by the shakedetection sensor 101 is ideally corrected, and time-series data of ashake correction amount when the offset in FIG. 6D is applied. Theoffset table in FIG. 6D is set so that the offset amount graduallyincreases from a small shake correction amount to a large one not toabruptly increase the offset amount from a given range of the shakecorrection amount. In range A, the offset-applied shake correctionamount is smaller than the ideal value of the shake correction amountowing to the influence of the offset, and the shake remains. Even inrange B, the shake is generated to exceed the movable range of imageblur correction, and the shake remains by the difference between theoffset-applied shake correction amount and the ideal value of the shakecorrection amount. However, unlike FIG. 6A, the offset value to returnto the center does not abruptly increase even if the shake correctionamount exceeds a given image blur correction range. The differencebetween the ideal value of the shake correction amount and the shakecorrection amount increases gradually. This prevents an abrupt change ofthe differential value of the difference between the ideal value of theshake correction amount and the shake correction amount, that is, themotion vector of the image on the image sensor. Hence, when a man viewsthe image in range B, he feels the shake to be less uncomfortable inFIG. 6C than in FIG. 6A.

From this, as the offset table, a table which gradually increases theoffset amount from a small shake correction amount to a large one, likeFIG. 6D, is preferable to a table which abruptly changes the offsetamount from a given range, like FIG. 6B.

However, if the gradient of the offset table is excessively gradual in atable as shown in FIG. 6D, the image blur exceeds the movable range ofimage blur correction in range B. To the contrary, if the gradient ofthe offset table is excessively steep, the remaining amount of the imageblur in range A becomes large, impairing the shake reduction effect.

Considering this, the effects of the shake correction apparatus in thefirst embodiment will be explained with reference to FIGS. 7A to 7D.FIG. 7A shows time-series data of an ideal shake correction amount whenthe shake of the image capture apparatus that is detected by the shakedetection sensor 101 is ideally corrected, and time-series data of ashake correction amount when Offset Table 1 in the offset table of FIG.7D is applied. Offset Table 1 in the offset table of FIG. 7D sets arelatively large offset amount. When the shake amount is small, theshake reduction effect becomes weak, leaving the shake. However, whenthe camera shake is larger than the movable range of image blurcorrection, it is optimally controlled within the range of image blurcorrection.

FIG. 7B shows time-series data of an ideal shake correction amount whenthe shake of the image capture apparatus that is detected by the shakedetection sensor 101 is ideally corrected, and time-series data of ashake correction amount when Offset Table 2 in the offset table of FIG.7D is applied. Offset Table 2 in the offset table of FIG. 7D sets arelatively small offset amount. When the shake amount is small, theshake reduction effect is good, hardly leaving the shake. However, whenthe camera shake is larger than the movable range of shake correction,it is clamped at the upper and lower limit values of the movable rangeof shake correction, impairing the image stabilizing effect.

FIG. 7C shows time-series data of an ideal shake correction amount whenthe shake of the image capture apparatus that is detected by the shakedetection sensor 101 is ideally corrected, and time-series data of ashake correction amount when control to switch between Offset Table 1and Offset Table 2 in the offset table of FIG. 79 is applied. OffsetTable 1 and Offset Table 2 are switched in accordance with a shake levelcalculated by the shake state determination unit 114. In a time periodduring which the shake is small, Offset Table 2 is applied to enhancethe shake reduction effect and hardly leave the image blur. In a timeperiod during which the shake is large, Offset Table 1 is applied tooptimally control the shake within the movable range of image blurcorrection.

In this fashion, according to the first embodiment, several set offsettables are switched in accordance with a shake level calculated from theangular velocity. The shake correction effect can be optimized withinthe movable range of image blur correction in both a state in which theshake is large during walking or the like, and a state in which theshake is small.

Second Embodiment

The operation of a shake state determination unit 114 in the secondembodiment of the present invention will be described. FIG. 8 is aflowchart showing the internal operation of the shake statedetermination unit 114 in the second embodiment. FIGS. 9A to 9C showtime-series data of a shake level calculated by the shake statedetermination unit 114 in the second embodiment. Note that processing tobe described below with reference to FIG. 8 is repetitively executed inevery sampling cycle during a predetermined period.

In step S201, the shake state determination unit 114 determines whetherInitFlag has been set. If InitFlag has not been set, the shake statedetermination unit 114 sets InitFlag in step S202, sets 0 in a shakestate determination counter ShakeLevelCnt in step S203, and thenadvances to step S204. Once InitFlag is set, the process branches tostep S204 after the determination in step S201 in the next cycle. Notethat this process starts when the image stabilizing operation is ON.When the image stabilizing operation is OFF, InitFlag is initialized,and when the image stabilizing operation starts, the determination instep S201 is performed again, and InitFlag is set in step S202.

If the shake state determination unit 114 determines in step S201 thatInitFlag has been set, it advances to step S204 to calculate theabsolute value GyroAbS of an angular velocity Gyro output from an HPF103. If GyroABS is larger than a predetermined threshold Thresh1 in stepS205, the shake state determination unit 114 advances to step S206. IfShakeLevelCnt is smaller than the upper limit value ShakeLimit of theshake state determination counter in step S206, the shake statedetermination unit 114 advances to step S207. In step S207, the shakestate determination unit 114 adds a predetermined count-up value CntA toShakeLevelCnt, ends the process, and waits for the next sampling cycle.If ShakeLevelCnt is equal to or larger than ShakeLimit in step S206, theshake state determination unit 114 ends the process and waits for thenext sampling cycle.

If GyroABS is equal to or smaller than Thresh1 (equal to or smaller thanthe threshold) in step S205, the shake state determination unit 114determines in step S208 whether ShakeLevelCnt is larger than 0. IfShakeLevelCnt is larger than 0, the shake state determination unit 114subtracts a predetermined count-down value CntB from ShakeLevelCnt instep S209, ends the process, and waits for the next sampling cycle. IfShakeLevelCnt is equal to or smaller than 0 in step S208, the shakestate determination unit 114 sets 0 in ShakeLevelCnt in step S210, endsthe process, and waits for the next sampling cycle.

FIGS. 9A to 9C show time-series data of a shake level calculated by theshake state determination unit 114 in the second embodiment. FIG. 9Ashows an angular velocity signal output from the HPF 103. FIG. 9B showsan angular velocity absolute value obtained by converting an angularvelocity signal into an absolute value. FIG. 9C shows time-series dataof ShakeLevelCnt described with reference to FIG. 8, which is a shakelevel output from the shake state determination unit 114 in the secondembodiment.

The amplitude of the detected angular velocity is small during timeΔTime1, and the camera shake is small because the user captures an imagewhile holding the image capture apparatus with his hands not to shakeit. The amplitude of the detected angular velocity is large during timeΔTime2, and the camera shake is very large owing to image capturingduring walking or the like. During time ΔTime3, the amplitude of theangular velocity is an intermediate one between that during ΔTime1 andthat during ΔTime2. During time ΔTime4, the user intentionally moves theimage capture apparatus to, for example, change its composition.

In this fashion, a shake level signal as shown in FIG. 9C can bedetected by control processing in FIG. 8, and it can be detected whetherthe shake is large in an image capturing state such as image capturingduring walking. Further, the shake level signal can be detected by asimple arrangement without using a filter arrangement like the shakestate determination unit 114 in the first embodiment.

Third Embodiment

The operations of a shake state determination unit 114 and offsetcalculation unit 115 in the third embodiment of the present inventionwill be described. FIG. 10 is a block diagram showing the arrangement ofa shake correction apparatus according to the third embodiment of thepresent invention.

The offset calculation unit 115 generates a signal for returning theshake correction amount to the correction center position in accordancewith a shake level from the shake state determination unit 114, and ashake correction amount calculated by a target position calculation unit108. Then, the offset calculation unit 115 outputs the signal to asubtracter 104 serving as an offset application means.

The shake correction amount of a preceding cycle that is calculated bythe target position calculation unit 108 is input to an offset table301, outputting an offset value corresponding to a set table. The offsettable 301 is a 1-input 1-output table.

After that, a variable gain calculation unit 302 calculates, based onthe shake level from the shake state determination unit 114, a gain tobe added to an offset value output from the offset table 301. Forexample, the variable gain is set as shown in FIG. 11. The offset valueis multiplied by a variable gain 303, outputting the resultant offsetvalue to the subtracter 104 serving as an offset application means.

According to the third embodiment, an offset amount corresponding to theshake level can be calculated. The shake correction effect can beoptimized within the movable range of image blur correction in both astate in which the shake is large during walking or the like, and astate in which the shake is small. A 3D offset table as in the firstembodiment need not be adopted, and the image stabilizing effect can beoptimized by using a 1-input 1-output 2D offset table and one variablegain without increasing the ROM capacity for the CPU.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2010-024827, filed Feb. 5, 2010, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image blur correction apparatus comprising: ashake detection unit which detects a shake; a calculation unit whichcalculates an image blur correction amount that is data for correctingan image blur which is caused by the shake and is obtained byintegrating output signal of said shake detection unit that is speeddata detected by said shake detection unit by an integration unit; animage blur correction unit which corrects the image blur based on theimage blur correction amount calculated by said calculation unit; ashake level determination unit which determines a shake level of animage capturing apparatus based on an output of said shake detectionunit; a subtraction unit which subtracts an offset value, which is speeddata for returning said image blur correction unit to a center of amovable range of said image blur correction unit, from speed data outputfrom said shake detection unit; and a changing unit which changes theoffset value based on the image blur correction amount and the shakelevel.
 2. The apparatus according to claim 1, wherein in a case that theimage blur correction amount is larger than a predetermined value, saidchanging unit sets the offset value larger than the offset value whichis set in a case that the image blur correction amount is not largerthan the predetermined value.
 3. The apparatus according to claim 1,wherein in a case that the shake level is larger than a predeterminedvalue, said changing unit sets the offset value larger than the offsetvalue which is set in a case that the shake level is not larger than thepredetermined value.
 4. An optical apparatus comprising the image blurcorrection apparatus according to claim
 1. 5. An image capturingapparatus comprising the image blur correction apparatus according toclaim
 1. 6. A method of controlling an image blur correction apparatuscomprising: a shake detection step of detecting a shake; a calculationstep of calculating an image blur correction amount that is data forcorrecting an image blur which is caused by the shake and is obtained byintegrating output signal of said shake detection unit that is speeddata detected by said shake detection step; an image blur correctionstep of correcting the image blur based on the image blur correctionamount calculated by said calculation step by an image blur correctionunit; a shake level determination step of determining a shake level ofan image capturing apparatus based on an output of said shake detectionstep; a subtraction step of subtracting an offset value, which is speeddata for returning the image blur correction unit to a center of amovable range of the image blur correction unit, from speed data outputfrom said shake detection step; and a changing step of changing theoffset value based on the image blur correction amount and the shakelevel.
 7. A shake correction apparatus comprising: a shake detectionunit which detects a shake; a calculation unit which calculates a shakecorrection amount for correcting an image blur based on an output fromsaid shake detection unit; a shake correction unit which corrects theimage blur based on the shake correction amount; a shake leveldetermination unit which determines a shake level of the shake based onan output from said shake detection unit; an offset determination unitwhich determines an offset value based on the shake correction amountand the shake level; and a subtraction unit which subtracts the offsetvalue from the output from said shake detection unit, wherein the offsetvalue is data for returning said shake correction unit to a center of amovable range of said shake correction unit, and wherein said offsetdetermination unit increases the offset value in a case where the shakelevel is larger than a predetermined level comparing with a case wherethe shake level is equal to or smaller than the predetermined level, ina whole area of a movable range of image blur correction of the shakecorrection unit.
 8. The apparatus according to claim 7, wherein the casewhere the shake level is larger than the predetermined level correspondsto moving image capturing during walking and the case where the shakelevel is equal to or smaller than the predetermined level corresponds tohandheld moving image capturing.
 9. The apparatus according to claim 7,wherein in the case where the shake level is larger than thepredetermined level, said offset determination unit determines theoffset value such that the shake correction amount falls within a rangein which said shake correction unit can move.
 10. A method ofcontrolling a shake correction apparatus including a shake correctionunit which corrects an image blur, the method comprising: a shakedetection step of detecting a shake; a calculation step of calculating ashake correction amount for correcting an image blur based on an outputfrom the shake detection step; a shake correction step of driving theshake correction unit based on the shake correction amount; a shakelevel determination step of determining a shake level of the shake basedon an output from the shake detection step; an offset determination stepof determining an offset value based on the shake correction amount andthe shake level; and a subtraction step of subtracting the offset valuefrom the output from the shake detection step, wherein the offset valueis data for returning said shake correction unit to a center of amovable range of said shake correction unit, and wherein said offsetdetermination step increases the offset value in a case where the shakelevel is larger than a predetermined level comparing with a case wherethe shake level is equal to or smaller than the predetermined level, ina whole area of a movable range of image blur correction of the shakecorrection unit.
 11. An image blur correction apparatus comprising: ashake detection unit which detects a shake; a calculation unit whichcalculates an image blur correction amount that is data for correctingan image blur which is caused by the shake and is obtained byintegrating output signal of said shake detection unit that is speeddata detected by said shake detection unit by an integration unit; animage blur correction unit which corrects the image blur based on theimage blur correction amount calculated by said calculation unit; ashake level determination unit which determines a shake level of animage capturing apparatus based on an output of said shake detectionunit; a subtraction unit which subtracts an offset value, which is speeddata for moving returning said image blur correction unit to a center ofa movable range of said image blur correction unit, from speed dataoutput from said shake detection unit; and a changing unit which changesthe offset value based on the image blur correction amount and the shakelevel, in a whole area of a movable range of said image blur correctionunit.
 12. The apparatus according to claim 11, wherein in a case thatthe image blur correction amount is larger than a predetermined value,said changing unit sets the offset value larger than the offset valuewhich is set in a case that the image blur correction amount is notlarger than the predetermined value.
 13. The apparatus according toclaim 11, wherein in a case that the shake level is larger than apredetermined value, said changing unit sets the offset value largerthan the offset value which is set in a case that the shake level is notlarger than the predetermined value.
 14. An optical apparatus comprisingthe image blur correction apparatus according to claim
 11. 15. An imagecapturing apparatus comprising the image blur correction apparatusaccording to claim
 11. 16. A method of controlling an image blurcorrection apparatus comprising: a shake detection step of detecting ashake; a calculation step of calculating an image blur correction amountthat is data for correcting an image blur which is caused by the shakeand is obtained by integrating output signal of said shake detectionunit that is speed data detected by said shake detection step; an imageblur correction step of correcting the image blur based on the imageblur correction amount calculated by said calculation step by an imageblur correction unit; a shake level determination step of determining ashake level of an image capturing apparatus based on an output of saidshake detection step; a subtraction step of subtracting an offset value,which is speed data for returning the image blur correction unit to acenter of a movable range of the image blur correction unit, from speeddata output from said shake detection step; and a changing step ofchanging the offset value based on the image blur correction amount andthe shake level, in a whole area of a movable range of the image blurcorrection unit.